Testing and sorting control system



April 21, '1953 L. L GoRDoIN l 2,635,746

TESTING AND SORTING CONTROL SYSTEM )NVE/vm@ LLOYD L. GORDON ATTORNE YSApril 2l, 1953 L. L. GORDON TESTING AND soRTING coNTRoL SYSTEM 4sheets-sheet 2 Filed June 25, 1949 /N VEA/TOR LL Oy@ L. GRON BV awk/MAM,h/ff* ATTVEYS April 21, 1953 L. L, GORDON 2,635,746

TESTING AND SORTING CONTROL SYSTEM Filed June 25, 1949 4 Sheet'sSheet 5FIG. 3A FIG. 30

PIIoofcE-LI. ourPur l peur Mv. ourpur x- TIME a FIG .3B FIG. 3L'

AMPLIFIER rz ouTPuv y-MJD 1E MM ouTPur F/G- 3C FIG. 3F SYNCHRON/ZINGIUPUI-SE REJECT DELAY MJ( OU'lTl/ TIME rme FLAWLESS OBJECT FLAWED OBJECTFIG. 4A F/O.4D

MIC AMF INPUT fr- TIME P*- xr/Me F /G- 4C L FIG. 4F IMF ai LEVEL orACCEPTANCE l- E TIME r/ME /Nl/ENTOR LLOYD L GORDON BOV 43m, W,

AT TORNE YS April 21, 1953 L. 1 GORDON 2,635,746

TESTING AND soRTING CONTROL SYSTEM Filed June 25, 1949 4 Sheets-Sheet 4F IG.v .5

J n lilno 7/5 /08 /7/ [/02 /o7L- 72 (1 l AA; mcRoPHoNE- AMPLIFIER I l l(/03 -/04 /l0 \/4 y \r9 I( V/as ,of

A TTOR/VE' YS Patented Apr. 21, 1953 UNITED TESTING AND SORTING CONTROLSYSTEM Libya L. Gordon, West End, N. J., assignor to ElectronicAssociates, Inc., Long Branch, N. J., a corporation of New JerseyApplication June 25, 1949, Serial No. 101,472

v 'mechanical defects. To this end the apparatus ,includes a striker forthe percussive, impulsive initiation of mechanical vibrations in eachVobject, an electromechanical transducer-responsive to the Vibrations ofthe object,`and` electrical apparatus for the automatic'determination of,the inner energy consumption lor natural vibration frequency of thevibrating object as it moves along the'test conveyor. The' comparison ofeither characteristic with a predetermined stand- VardY then serves as abasis for rejecting or passing `the object under test.

The present invention contemplates novel cir- ;cuit arrangements usefulparticularly in connection withv the apparatus of the above-referencedapplication. The circuit arrangementsV include control circuits for thevibrationinducing mech- .anism, synchronizing circuits for actuating thetransducer for a predetermined intervalV of time Iafter the. initiationof vibrations in an object, ,comparator circuits for comparing theamplitude Yorfthe. frequency of the signals from the transducerWithastandard, and circuits for actuating ir'idi'catingV or `rejectionapparatus when an object generates signals which fail tomeetthat'standard. In a particular embodiment of the invention there isincludeda gaseous discharge device controlling a capacitor dischargecircuit for the preoise control of the -actionvof the strikerjandrforAthe generation of a synchronizing impulse at the time of action, adelay multivibrator for generating an impulse at a given time intervalafter the vsync'lfironizing signal, a switching circuit for activatingthe transducer circuit and controlled by 'a gating signal generatorwhich is, in turn, re-

sponsive to the impulse from the multivibrator, 'a reject apparatuscontrol circuit utilizing a gaseous discharge device, an impulsegenerator `connected to the multivibrator for normally impressing an'actuating impulse upon a control electrode of the gaseous dischargedevice at a time when the object under test is in a position for theaction of the reject apparatus, and a Claims. (Cl. 209-72) that thetolerance range of differentiation between acceptable and unacceptableobjects may be adjusted within a' wide range, and that the circuitarrangements are highly stable in operation and are suitable forcontinuous operation under production conditions.

The invention, together with the objects and further advantages thereof,may be better understood by reference to the following detaileddescription taken in connection with the accompanying drawings, inwhich:

Fig. 1 is a schematic diagram of the circuit and associated apparatus ofthe invention;

Fig. 2 is a detailed diagram of the circuit of the invention; Y

Fig. 3 is a representation of lthe waveforms of the circuit of Fig. 2;

rFig. 4 is a representation of the vibrations and signals produced byflawless and awed objects;

and

Fig. 5 is a diagram of a modification of the circuit of Fig. 2.

n Referring now to Fig. l, thereis shown a conveyor i suitable forcarrying an object to be tested, such as, for example, an architecturaltile i2.' The test conveyor l is shown as part of a typical Yarrangementin which a second conveyor 3` carries the object tobe tested from theprior production operations to the test conveyor I. A third conveyor d.may be utilized to carry those objects of requisite quality on tofurther production operations. Conveyor l may travel at apredetermined'uniform rate of speed, while conveyor 3 is driven at aspeed such that the objects 'to be tested are delivered to conveyor I ina suiiiciently spaced fashion.

A lamp 5 acts as a light source, the light being formed into a narrowbeam directed transversely A photoelectrc cell 6 is disposed oppositethe'la'mp 5 in a manner such that the light beam normally falls upon acathode 'l of the cell 6 but is interrupted by the passage yof 'theobject to be tested along the conveyor.

The cathode l and an anode 8 of the photoelec" tric cell 6 are connectedto an amplifier 9 which vserves to actuate a striker control circuit it)upon the interruption of the light beam by the object. The strikercontrol circuit l0, when actuated by the impulse from the amplier 9,supplies a pulse of current to a coil of a striker l2 which causes anarmature I3 to strike the object 2 a sharp blow of an intensitydetermined by the amount of energy supplied to the coil of the solenoid.The impact of the blowr by the armature I3 thus imparts to the object 2an impulse excitation which induces a train of damped, free mechanicalvibrations in the object. Y

The vibrating object under test moves along'the test conveyor l until itreaches a position adjacent a microphone I4. As explained in application Serial No. 101,471 above mentioned, the conveyor I may preferablybe of a design and construction such that the rate of decayfof thearnpltude of the vibrations or" Vthe object under test is determinedsubstantially by the inner energy dissipation of the object under test,the energy dissipation due to the conveyor being `small compared to theenergy dissipation inherent vthe object. Under such conditions, theelapse of time during which the .obiect tre-vele from the lnosltioii atwhich the vibrations are induced toa position ecliecent the microphoneVi4 will result in a flecreese .in the amplitude oi the vibrations ofthe object, the amount of decrease being determined by the inner energyconsumption, or, equivalently, the mechanical quality of the object. Inoperation, the microphone i4 serves as an electro.- mechehicaltransducer .to convert the .sound Waves produced .by the Vibratingobject into electrieal variations having characteristics corre-.Spending to those .of the vibrations of the .object under test. Thecharacteristics of the electrical variations may then be vutilized as abasis by which the ,defective Vobjects may be separated from .those ofsatisfactory .quality- The striker control circuit i3, when .actuatingthe striker solenoid l2, simultaneously generates ou impulse which.serves es `a synchronizing or timing impulse for the control of thesubsequent operations. The timing pulse is effectively V`delayed in timeby a delay circuit I5 which may be a delay multivibrator of known typeor a functionally similar arrangement. The `output of the delay circuitE5 is then utilized to control a gate signal generator I3 which producesan impulse of predetermined duration. This impulse is ampli.- fled by `agate amplifier I'.' to deactuate a Arelay I8 which in turn renders thecircuitof the micro.- phone j!! active for the duration of the impulse.The time delay introduced by the del-ay circuit vIii is such that themicrophone I4 is active only after e period in which themoSteighif-ce-ht changes in the vibration characteristcs have takenplace, as is more fully described below.

The electrical Variations produced by the microphone il! during theactive period are am.- plied by an amplier l2. The output of the am.-pli-er is connected to a signal comparator 2,0 which determines thecharacteristics o f the electrical variations arriving from amplier VI9.Thus the :comparator may be arranged to lproduce an output signal orimpulse if the input signal exceeds a predetermined amplitude level, butnot to do so if the input signal is below that level.

A reject control circuit i2| is arranged to beresponsive both to signalsfrom the signal comparator 20 and a reject delay circuit 22. The rejectdelay circuit 22 is controlled bythe impulses from the dele-y circuit leto produce impulses of a rredetermined duration and which are delayed intime with respect to the impulses from the delay circuit i5. Thesepulses from reject delay 22 actuate reject control 2| for each object.The reject control circuit 2| may then be arranged so that for objectswhich produce signals at the output of the comparator 20, the rejectcontrol 2| remains inactive, Whereas for objects which do not produce asignal at the output of the comparator the reject control actuates thesolenoid 23 of suitable reject mechanism. The solenoid 23 is connectedto a reject mechanism such as, for example, the tra-p 24, so 'thatdefective objects do 'not reach the conveyor 4.

Proceeding now to a more detailed description oi" the invention,reference may be made to Fig.

`A2 Which shows a schematic diagram of the circuits of the invention.The description of the schematic diagram Yvirili .be given also withreference to the functimial diagram of Fig. 1.

The photoelectric cell 5 of Fig. 21s connected to an amplier including atube TI corresponding in function to the amplifier 9 of Fig. l. Theanode J .of the photoelectric cell is connected to a voltage dividercomprising a resistor 25 and a potentiometer 2.6 `and YSupplied by a:source of high potential, conventionally .represented as .a batter-y21. The cathode 8 of thephotoeleotric cell is .connected to a .grid .2Bof tube Tj, the grid being connected to .ground through a resistor .29.Anode `3 0 of tube Tl 4is .energized by the battery 2l :through an anodecoupling resistor 3| While a cathode 32 -is `connected to .thepotentiometer .2.6 which provides a variable .source Yof cathode biaspotential. In operation, the Yinterruption .of the light from the sourceA5r falling .upon the photoelectric cell by the object 2 under .test.causes a sharp decrease inthe Vpoten-tial of the grid 28 of tube TThere Vis thus produced an-abrupt in.- .crease in the potential of theanode 30.

The function of the striker control circuit |.0 of Fig. 1 is performedby tubes T2 and T3 .of Fig. ,2. The positive potential change at theanode `3|) .of tube Tl is impressed through a coupling condenser 3.3upon a control grid .34 of tube T2 which acts as a cathode-Coupled'amplien TheV grid 34 is connected through a resistor 35 to the cathodecoupling resistors :3.6 and 3l which .are .connected between ycathode 38of tube T2 and the common ground lead and negative pole of the potentialsource Vit'l. The `positive change in potential of lthe cathode 38 dueto the positive impulse upon the grid 34 is communicated through acoupling condenser 39 to la control grid 40 of a gaseous dischargedevice T3. Anode 4| of tube T3 is convnected through thecoil of thestriker |2 to a condenser 42 which is charged Vfrom the potential source27 by means of a resistor 43 which serves also as a current limitingresistor when the tube T3 is in e conducting condition. A resistor 44 1sconnected from the control grid 40 to a source 45 of bias potentialwhich serves Ato keep the tube T3 in a normally non-conductingcondition. Cathode 4E of tube T3 is connected to ground through a coil41 Which serves as an impedance across which a sharp positivesynchronizing impulse is generated when the tube is fired by a positiveimpulse upon the control grid 40. In operation the tube T3 is red by thepositive impulse from tube T2 so that the condenser 42 dischargesthrough the coil I I of the solenoid |2. The positive impulse from tubeT2 ceases before the discharge is completed so that at such a time asthe condenser 42 is sumciently discharged the tube T3 becomesnon-conducting due to the deionization of the gaseous medium. Thecondenser 42 is then recharged. The gaseous discharge device T3 thusserves to actuate the striker solenoid l2 when the object 2 is in theproper position while atv the same time providing a synchronizing pulsefor the control of subsequent operations.

The function of the delay circuit vi5 of Fig. l is performed by tubes T4and T5 of Fig. 2 and the circuits associated therewith. Tubes T4 and T5are connected so as to form a single impulse multivibrator having acycle which is initiated by the synchronizing pulse generated in thecathode circuit of tube T3. The synchronizing impulse from the cathodecircuit of tube T3 is impressed upon a control grid 48 of tube T4 whichis ina normally non-conducting condition. 4The Apositive impulse uponthe grid 48 causes the tube T4 to conduct, thus causing a decrease inthe potential of anode i9, the negative impulse being imparted to acontrol Igrid 59 of tube TbA by means of a coupling condenser 5I. TubeT5 becomes non-conducting and, due to the fact that the cessation ofcurrent flow through the tube T5 causes a, decrease in the potentialdrop across the common cathode coupling resistor 52 and hence increasesthe conductivity of the tube T4, the circuit remains stable in thiscondition. 'Ilube Tllcontinues in a conducting condition and tube T5 ina non-conducting condition until the coupling condenser 5I is dischargedby the grid resistor 53 to a potential such that the control grid 50 oftube T5 allows that tube to again become conducting and tube-T4 returns.to the nonconducting state. There is thus formed at the anode 54 oftube T5 a positive potential pulse having a duration determinedessentially by the condenser 5I and by the adjustment of resistor 53.

'Ihe function of the gate signal generator I5 (Fig. l) is performed bytubes T5 and T1 and the circuits associatedr therewith. Tlubes T6 and T1are connected to form arsingleimpulse cathode-coupled multivibratorsimilar in all essential respects to that formed by the tubes Trl and T5with the exception that the Ygrid input circuit of tube T5 is soarranged that tube T5 is normally conducting while tube T1 is normallynon-conducting. The positive potential pulse formedatV the anode 54 oftube T5 is imparted to contror grid 55 of tube T03 by means of acoupling con denser 5E. The coupling condenser55 and the associated gridresistor IIIhave a. time constant such that, at ther cessation of thepositive virnpulse from tube T57 the control grid 55 is driven negative,thus rendering tube T5 non-conducting. The potential of the anode 51 oftube T6Y thus becomes more positive, the positive impulse beingcommunicated to a control grid 5,3 of tube'T by means of a couplingcondenser 59. Tube T1 then becomes conducting and remains in thatlcondition until the coupling condenser 59 is suicient'ly discharged bygrid resistor SI1. There is thus formed at the anode 6I of tube T1 anegative potential pulse which is initiated at essentially the same timeas the cessation ofthe positive pulse at the anode 5 of tube T5 andhaving a-duration determined essentially by the size of the couplingcondenser 59 and the adjustment of the resistor 6G.

Tube T8 serves as the gate amplifier I! of Fig. 1. The negativepotential impulse formed at the anode 6I of tube T1 is imparted throughthe coupling condenser 62 to the control-grid 83 .of tube T8. Anode S5`of tube T8 is connected through a current limiting resistor 55 and thefield coil of relay 'IB to the positive-pole of the source of highpotential 21; 'Ihe contacts of the relay 55 and E1 are held in a closedposition by the normal anode current of the tube T8 so that the negativepotential 'impulse Whichis applied to the. grid 63 decreases the anodecurrent, thus opening the contacts and activating the circuit 'of themicrophone I 4.

Returning now to the object under test, it will be seen that, due to theintensity of the impulsive excitation imparted by the striker I2, theobject will continue in mechanical vibration as it moves along theconveyor to a position under themicrophone. The sound waves produced bythe mechanical vibrations of the object are imparted to the microphonewhich in turn generates a train of damped electrical vibrations havingamplitude and frequency characteristics corresponding substantially tothe amplitude and frequency characteristics of the mechanical vibrationsof the object under test. The microphone I4 is connected through theYcontacts 66 and 61 of the relay I8 so as to be normally grounded. Ashas previously been explained, however, the relay I8 is opened so as toactivate the microphone Id after a suit-able time delay introduced bythe delay multivibrator formed by tubes T4 and T5. It is thus necessarythat the conveyor I travel at a relatively constant rate of speed andthat the delay between the action of the striker I2 and the :activationof the microphone I4 correspond to that speed.

During those periods in which the microphone I5 is active, theelectrical variations are amplied by tube T9 which is a linear amplifiercorresponding in function to the amplifier I9 of Fig. 1. The variations:are impressed through a resistor 68 and a potentiometer 68 upon controlgrid 'iii of the tube T9, While the amplified variations appearing atanode 1I are impressed through a coupling condenser 12 upon controlgrid' of tube TI. f

Tubes TIU and Ti I and the circuits associated therewith perform thefunctions of the Vsignal comparator 2B of Fig. l. In the presentembodiment of the invention, this yfunction comprises the measurement ofthe amplitude of the signal Variations received from the anode 1I oftube T9 and the generation of a potential impulse if the signalamplitude exceeds a predetermined value or standard. Tubes TIG and TIIare normally conducting, tube TIB normally having a somewhat greateranode current than tube TI I. The control grid 13 and the cathode 14 oftube TIE) in conjunction with the grid resistor 15 and the cathodepotentiometer 'i6 serves in eiect as a biased rectifier or detector. Inoperation, those portions of the amplified signal which 'are 'of anamplitude greater than the value of the bias are rectified and theresulting voltage which is formed across the grid resistor 15 is addedto the value of bias normally determined by the adjustment of thecathode potentiometer 16. As the eiective bias on the control grid 13increases, the anode current decreases so that the potential of theanode 11 becomes more positive. This p0- tential change is communicatedto the control grid 19 of tube TI I by means of the coupling condenser18 causing theganode current of tube TII to increase and the potentialof the anode 8E! to decrease. Due to the presence of a common cathodecoupling potentiometer 16, the increase in anode current of tube TII'causes a further increase in the potential of the anode 'I1 of tube TI Iand the proces'scontinues until such time as a saturation point isreached. There is thus formed a strong negative potential impulse at theanode 83 of tube TI I. A condenser BI serves to eliminateany signalvariations which may have been incorporated-in the impulse. y

`if the amplitude of the signal variations impressed upon the controlgrid 'I3 of tube TIe is less than the value of bias determined by theadjustment of the potentiometer l there is no signal rectification.There is, therefore., no change in the bias of the tube .TI Il, ,and nopotential irnpulse is formed at the anode Si! of tube T I I.

The function of the reject control circuit 2| of Fig. l is performed bytube TI2 and the circuits associated therewith. Tube TI 2 is a gaseousdischarge device having an anode 2.2 connected through the solenoid 23to a condenser 83 which is charged through a current limiting resistor84 by the potential source 2l. Condenser es is proportioned so as toenergize the solenoid 23 only for the desired period of time. At the endof the desired time the potential across the condenser must reach avalue such that the tube T52 becomes deionized and the entire cycle maythen be repeated for another object. The grids 85 and 8S of tube TI2 areconnected through grid resistors 81 and 38 respectively to a source .83or bias potential, the bias being of a magnitude suilicient to maintainthe device in a normally non-conducting condition. The grid SE iscoupled to the anode 88' of tube TII by means of a coupling condenser9i) so as to impress the negative impulses generated at the anode 8Gupon the grid 85.

The action of tube TI2 is controlled not only by the negative potentialimpulses from tube TI I but also by impulses from tube TM. Tube TM, andtube TI 3 form a single impulse multivibrator responsive to the positiveimpulses generated by tube T5 and perform the function of the rejectdelay circuit 22 oi Fig. 1. The positive impulses from the anode 5s oftube T5 are impressed upon control grid SI of tube TLS through acoupling condenser 92. Tube TIS is normally in a conducting conditionand condenser S2 and grid resistor 93 are proportioned so that the gridBI is driven negative and the tube rendered non-conducting at thecessation of the positive exciting impulse. Tube TILG then becomesconducting and remains in the conducting condition until the couplingcondenser 94 is suniciently discharged. There is thus formed at theanode 95 of tube TI!! a negative potential impulse which is initiated atessentially the same time as the cessation -of the positive pulse at theanode 54 of tube T5 and having a duration determined by the size of thecoupling condenser 2li and the adjustment of the associated variablegrid resistor I I2. The negative impulse thus formed is impressedthrough a coupling condenser 9S upon the grid 86 of tube TI2.

The control of the action of tube TI 2 by the impulses from tubes TI Iand TM depends essentially upon the simultaneous occurrence of thoseimpulses. The coupling condenser 96 and grid resistor 8S are of suchvalues that they act as a differentiator for the negative potentialimpulses communicated from the anode 95 of tube TIA to the grid 86 oftube TI2. Hence, at the cessation of the pulse the grid 86 becomessufficiently positive so that tube TI2 would normally fire. If, however,the object under test is of a quality such that the vibrations have notbeen excessively dissipated before the microphone I4 is activated, theaction of tubes TIB and TII` will serve to generate a negative impulselwhich is impressed upon the grid 85 of tube TEE, thereby counteractingeffect of the positive impulse upon the grid 8B, and the tube does notfire. In the event that the object under test is defective, thevibrations will. be dissipated to such an extent that, the signalimpressed upon the grid 'I3 of tube TI I3 will be less than the `normalbias and a negative impulse will not be impressed upon the grid 85. TubeTI2 Will then be fired by the impulse from tube TI4 and condenser 83will discharge into the solenoid 23.

The reject mechanism illustrated in Fig. 2 is an alternative to that ofFig. 1, similarly serving as a separating means in identifying thoseobjects which fail to meet the standard imposed by the adjustment of thetest apparatus. The mechanism comprises a reservoir 91 which is capableof holding a marking ud such as an ink, and preferably under pressure.The ovv of the uid is controlled by a valve S8 which is connected to anarmature 99 of the solenoid 23. The ring of tube TI2 by a defectiveobject thus energizes the solenoid 23 to open the valve S2 so that themarking uid is sprayed upon the defective object'. It is to beunderstood of course that the reject mechanism should be positionedquite closely to the microphone I4 since a very low order of time delayis introduced by the action of tubes T9 through TI2, in the embodimentdescribed.

it is an essential requirement in the operation of the apparatus of theinvention that the action of the striker I2 be uniform, that is, eachobject must receive a blow of uniform intensity. Accordingly, it will beunderstood that the use of the battery 21 as an energy source for thestorage capacitor 42 in Fig, 2 is purely conventional, it beingdesirable in practice to use a separate voltage-regulated power supply.

Referring now to Fig. 3, there is shown a series of sketches of thesignal waveforms of the illusf trative circuit of Fig. 2, the time-cycleshown being that for the testing of a single object. The waveforms ofFigs. S-A through 3-C are largely self-explanatory, the potentialsrepresented being those across the electrodes of the photocell ii; fromthe cathode 38 of tube T2 to ground; and from the cathode 48 of tube T3to ground; respectively. Fig. B-D represents the waveform of the outputof the multivibrator composed of tubes T4 and T5 of Fig. 2. The'duration or time-length of the impulse, denoted by X-time corresponds tothe delay of the synchronizing impulse by the delay circuit I5 of Fig.l, and, in the particular circuit of Fig. 2, is controlled by thepotentiometer 53. Fig. 3-E represents the Waveform of the output of themultivibrator composed of tubes T6 and T'I of Fig. 2, that is,`thegating signal formed by the gate signal generator I6 of Fig. 1. Theduration or. Y-time of the impulse determines the duration of activationof the microphone III and is controlled by the adjustment of thepotentiometer 60 of Fig. 2. Fig. S-F represents the Waveform of theoutput of the multivibrator composed of tubes TIB and TM of Fig. 2, theduration of the impulse corresponding functionally to the delayintroduced by the reject delay circuit 22 of Fig. l. It is to beunderstood of course that the waveforms shown are essentially schematicin nature.

Referring now -to Figs. 4A to 4C, inclusive, there are shown schematicrepresentations of the signals produced by objects, in the exemplarycase, architectural tile, which are relatively flawless as compared withthose produced by objects having serious mechanical flaws. Fig. 4-Ashows the nature of vibrationscf a relatively flawless object afterimpulsive excitation. vIt will be noted that these comprise a dampedtrain and that the rate of decrease of amplitude of successive cycles 9j of oscillation 1s relatively small, corresponding to a low internalenergy consumption in the object. Figure lp-D shows a train of .freeoscillations of an object Yhaving mechanical flaws, the decrement orrate of decrease of amplitude of successive cycles of oscillation beingrelatively high, corresponding -to a high internal energy .consumption.Figs. 4-B ands- E represent the electrical n signals corresponding tothe respective mechansignals at the output of the tube TI I of Fig. 2for theA two cases, respectively.

A consideration of Figures 4-A to 4-F, inclusive, will make clear anYessential feature and highly `important advantage of the circuits of theinvention. It will be realized that ordinary production variations ofobjects Ysuch as ceramicv tile may Vvary considerably, some beingsubstantially pervfect,others havingminor imperfections such as smallsurface cracks, while others may have serious defects. Since thelvariation of the inner energy consumption of the objects varies notonly as the magnitude of an individual flaw, but also according to thesum ofall iiaws, Whether large or small, the invention automaticallyprovides a measure-of all the flaws.- Due to shock excitation at theinstant of impact and for a few cycles thereafter -an excess ofharmonics is usually present, and these tend to mask the normalvibrations which truly represent the condition of the object. Since thepresent Ycircuit arrangement provides means for control of the elapseof? time between the initiation of vvibration andthe time of beginningof measurement, that is, X-time, and the number of'vibrations used as abasis'of comparison of amplitude, that is, Y-time, it will be seen thata precise determination of quality may be made within'as great or assmall vlimits of tolerance as is desired.

l The-embodiment of the invention thus far described employs the innerenergy consumption characteristic as a basis for distinguishing betweenacceptable or'unacceptable objects. As has been previously mentioned,the natural frequency of vibrationl may, in some applications be'used asVsuch a basis in applications where an object having internal.mechanical iiaws has a natural vibration rate differing substantiallyfrom that of a relatively flawless object. There is shown yin Fig. 5 acircuit useful as a modicator of the signal comparator circuit of Fig. 2to form an embodiment of the invention useful for such a method ofsorting or inspecting objects.

The circuit of Fig. 5 comprises a clipper IUI) and a frequency-selectiveamplifier II, the arrangement being intended for connection between theanode 'il of tube T9 and capacitor 'I2 of Fig. 2. The signal from theanode 1I is imparted through Ya coupling capacitor I2 to a half-waverectier serves to eliminate the portions of the positive half-cycles ofthe Wave-train whose amplitude is greater than a reference voltagegenerated by a voltage divider formed by resistors IUE and 166. There isthus impressed upon the grid VII of tube TIB a series of unidirectionalpulses of constant amplitude and of repetition rate equal to thefrequency of the impressed wave-train. `The anode H18 ofv tube T15 isconnected to a source of potential through an inductor H19 which,together with a capacitor lid, forms` a parallel-resonant circuit. Inoperation, the output of the amplier IBI lwill comprise essentiallysinusoidal waves whose amplitude will be strongly dependent upon therepetition rate of the impulses impressed upon the grid It? of tube TIE.The circuit formed by the inductcr |89 and the capacitor Il is adjustedto resonate at a frequency corresponding to the natural vibration rateof an acceptable specimenof the tile or object under test. Thus, fordefective objects, the amplitude of the signal impressed upon the gridof tube TIEI will be much lower than that of the acceptable objects,causingsuch defective units to be rejected in the manner previouslydescribed in connectionwith Fig. 21

It will nowbe apparent that the circuits of the invention embody manynovelfeatures which in coordinated relation and operation render anoptimum performance of the intended functions. It will be understood,however, Vthat the embodiment of the invention described herein is apresently preferred form and that many changes and Vmodifications indesign may be employed Without departing from the spirit and scope ofthe appended claims.

1 claim:

1. .In a sorting device, a conveyor for carrying objects to be sorted,means for impulsively initiating mechanical vibrations in each object,control circuits responsive to the position of an object along saidconveyor for generating synchronizing signals and for actuating saidvibration-initiating means, an electromechanical 'transducer` responsiveto the vibrations of the object for generating electrical signals,rejection means for designating the rejection of an object which causesthe generation of electrical signals different froma predeterminedvalue,a connecting circuit between said' transducer and said rejection means,activating means responsive to said synchronizing signals for activatingsaid connecting circuit, and delay-circuit means connected in saidconnection circuit between said transducer and said rejection means,said delaycircuit means being @adjusted to connect said transducer tosaid-'rejection means only for a predetermined period Aof timesubsequent to and exclusiveof the initiation .of vibrations in an objectby said vibration-initiating means.

2. In a sorting device, a conveyor for carrying the objects to besorted, control circuits for generating first and second synchronizingsignals, said circuits'being responsive to successive vposi- ,tions ofthe objects along said conveyor, means responsive to said iirstsynchronizing signals for impulsively initiating mechanical vibrationsin each object successively,- an `electromechanical .transducerresponsiveV to the vibrations of an object for generating electricalsignals, means for measuring the signals generated byisaid transducer toydetermine thelrelative quality of each object, rejection apparatuspositioned along said conveyor, a rejection control circuit for saidrejection apparatus-comprising a gaseous discharge device having atleast two control electrodes, means connecting said qualitydeterminingmeans to one control electrode of said discharge 11` device, and meansresponsive to said second synchronizing signals for impressing impulsesupon another control electrode of said discharge device.

3. The invention in accordance with claim 2, in which said last namedmeans comprises a delay circuit for form-ing an impulse a predeterminedlength of time after the occurrence of each synchronizing signal.

4. rThe invention in accordance with claim 2, in which said last namedmeans comprises a first signal impulse multivibrator, and which includesa second single impulse multivibrator responsive to the cessation of animpulse from said iirst multivibrator, and a diferentia-tor forgenerating a positive impulse upon the cessation or the impulse fromsaid second multivibrator.

5. In a sorting device, aconveyor for carrying the objects to be sorted,control circuit means for generating synchronizing signals, said circuitmeans being responsive to successive positions of the objects along saidconveyor, means responsive to said synchronizing signals for impulsivelyinitiating mechanical vibrations in each object, an electro-mechanicaltransducer responsive to the vibrations of an object for generatingelectrical signals, a signal comparator for generating impulses inresponse to signals from ilawless objects, delay-circuit meanscontrolled by said synchronizing signals connected between saidtransducer and said comparator andadjusted to transmit the electricalsignals from said transducer to said comparator a predetermined timeafter and including the initiation of vibrations in an object, rejectionapparatus connected to said comparator, and means responsive to saidsynchronizing signals for actuating said rejection Vapparatus only inthe absence of impulses from 'said comparator.

6.- In apparatus for sorting objects, a striker mechanism for inducingdamped mechanical vibrations in each object, a photoelectric controlcircuit responsive to the positioning of an Aobject adjacent saidstriker mechanism, a striker control circuit connected between saidphotoelectric circuit and said 'striker mechanism and being adapted toactuate said 4striker mechanism and simultaneouslyto generatesynchronizing signals, a microphone for generating electrical signals inresponse to the damped vibrations of an object, quality-determiningapparatus having any output voltage and connected to saidn'ric'zrophoneY forV comparingthe sign-als from said microphone With-astandard, time delay means responsive to each of said synchronizingsignals for generating a pulse a predetermined time subsequent to andexcluding the initiation of said electrical signals, means initiatingactuation of said quality-determining apparatus in response toVv saidpulse, rejection apparatus, and a circuit connected to saidquality-'determining apparatus for `actuating the rejection apparatuslin response to the output voltage of said quality-determining apparatus.

7. In apparatus for sorting objects, a conveyor, a striker mechanism forinducing a' train of damped mechanical vibrationsI in an objectpositioned on said conveyor, a phtoelectric control circuit respon'sive'to the positioning of an object in Iactuating relation to said strikermechanism, a striker control circuit connected between saidphotoelectric circuit and said striker mechanism, a microphone disposedadjacent said conveyor in position to be actuated'by vibrations from anobject thereon to produce electricalY signals, means for generating animpulse in response to said electrical signals when the. same are ofpredetermined characteristics, connecting means for transmitting saidelectrical signals to said impulse-generating means, time delay meansactuated by signals from said strikerv con; trol circuit connected toactuate said connecting means for a predetermined interval of timelessthan v the period of said train, a rejection control circuit connectedto sa-id impulse-'generating means, and means for actuating saidrejection control circuit only in the absence of an impulse from saidimpulse-'generating means.

8. In a device for sorting objects, means for generating a synchronizingsignal, vibration means actuated by said signal for impulsivelyinitiating a train of damped mechanical vibrations inan object, saidtrain being of a certain time period, an electromechanical transducerresponsive to the Vibrations of the object for generating electricalsignals corresponding to said vibrations, rejection apparatus, a controlcircuit connected to said rejection, apparatus to actuate the same, asignal comparator connected between said transducer and said controlcircuit,

.and time limiting Ymeans 'actuated by said syn/- Vthe objects to betested, means for impulsively initiating a train of damped mechanicalvibrations in each object, a synchronizing circuit for generatingsynchronizing signals, said circuit being responsive t-o successivepositions. of the ob.- jects along said conveyor for actuating saidvibration-initiating means,y a rst impulse generator responsive to thevibrationsof an object for generating an actuating impulse, delay meansactuated by said synchronizing signals for initiating the operation ofsaid generator only when the rate of decay of amplitude of thosevibrations is less than a predetermined value, a second impulsegenerator responsive to said synchronizing signals, rejection`apparatus, and a rejection control circuit connected to respond to bothsaid impulse generators so. as to actuate said rejection `apparatus inresponse to said actuating impulse in the absence of an impulse fromsaid first generator.

l0. The invention in accordance with claim 9 in which said rejectioncontrol circuit comprises a gaseous discharge device having a differentcontrol electrode connected to each impulse generator.l

1'1'. In asorting device, a conveyor for carrying objects to be sorted,ineansfor impulsively initiating mechanicalY vibrations' in each object,control circuits responsive to the position of an object along saidconveyor for generator synchronizing signals and for actuating saidvibration-initiating meanaanelectromechanical transducer responsive tothe vibrationof the object for generating electric signals, rejectionmeans for designating the rejection of an objectwhich; causes thegenerationl of electric signals different from a1 predetermined value, aconnecting circuit between said transducer and said rejectionmeans,activating means responsive to said synchronizing signals for activatingsaid connecting circuit only for a predetermined period oi time andsubsequent to and eirlusive of the initiation of'v the vibrations in anobject, the activating means for said connecting circuit comprising adelay circuit, a gate signal generator connected to the output of saiddelay circuit for generating a delayed gating impulse, andimpulse-operated switching means connected in said connecting circuiteiectively to open and close the same.

12. In a sorting device, a conveyor for carrying objects to be sorted,means for impulsively initiating mechanical vibrations in each object,control circuits responsive to theposition of an object along saidconveyor for generating synchronizing signals and for actuating saidvibration-initiating means, an electro-mechanical transducer responsiveto the vibration of the object for generating electric signals,rejection means for designating the rejection of an object which causesthe generation of electric signals different from a predetermined value,a connecting circuit between said transducer and said rejection means,activating means responsive to said synchronizing signals for activatingsaid connecting circuit only for a predetermined period of time andsubsequent to and exclusive of the initiation of the vibrations in anobject, the activating means for said connecting circuit including aiirst multivibrator and a second multivibrator responsive to thecessation of an impulse from said rst multivibrator and a relayresponsive to an impulse from said second multivibrator included in saidconnecting circuit.

13. In a device for sorting objects, means for impulsively initiating atrain of substantially free, damped, mechanical vibrations in an object,an electro-mechanical transducer responsive to the vibrations of theobject for generating electric signals corresponding to said vibrations,means for transmitting the signals from said transducer only for apredetermined period of time subsequent to the initiation of Vibrationsin the object, so as to include vibrations occurring substantially onlyin the central portion of said train, rejection apparatus, controlcircuits for actuating said rejection apparatus, and a signal comparatorconnected between said control circuits and said signal transmittingmeans operable to compare the characteristics of the electric signalswith a standard and to cancel the action of said control circuits whenthe signals meet that standard, said comparator comprising a clipper, afrequency selective amplifier, a bias detector and an impulse generatorin serial connection.

14. In a device for sorting objects, means for impulsively initiatingatrain of substantially free, damped, mechanical vibrations in anobject, an electro-mechanical transducer responsive to the 'vibrationsof the object for generating electric signals corresponding to saidvibrations, means for transmitting the signals from said transducer onlyfor a predetermined period of time subsequent to the initiation ofvibrations in the object as as to include vibrations occurringsubstantially only in the central portion of said train, rejectionapparatus, control circuits for actuating said rejection apparatus, anda signal comparator connected between said control circuits and saidsignal transmitting means operable to compare the characteristics of theelectrical signals with a predetermined standard and to cancel theaction of said control circuits when the signals meet that standard,said comparator comprising a signal amplitude limiter, afrequency-selective ampliiier, a circuit for passing signals of greaterthan a predetermined amplitude and an impulse generator in serialconnection.

15. In a device for sorting objects, means for impulsively initiating atrain of substantially free, damped, mechanical vibrations in an object,an electro-mechanical transducer responsive to the vibrations of theobject for generating electric signals corresponding to said vibrations,rejection apparatus and impulse-responsive control-circuit means foractuating the same, means including delay circuit means connectedbetween said transducer and said control circuit means for transmittingthe signals from said transducer to said control circuit means only fora predetermined period of time following and excluding the initiation ofvibrations in the object, the timing of said delay circuit means beingsuch as to transmit vibrations occurring substantially only in thecentral portion of said train, and a signal comparator connected betweensaid signal-transmitting means and said control circuit means, and beingoperable to compare the characteristics of the electric signals with apredetermined standard and to cancel the action of said control circuitmeans when the signals meet that standard, said comparator comprising abiased detector and an impulse generator controlled by signals from saiddetector.

LLOYD L. GORDON.

References Cited in the le of this patent UNITED STATES PATENTS NumberName Date 2,208,202 Stanton July 16, 1940 2,229,638 Chamberlin Jan. 28,1941 2,280,948 Gulliksen Apr. 28, 1942 2,357,512 Gaiser Sept. 5, 19442,393,225 Andalikiewicz Jan. 22, 1946 2,403,561 Smith July 9, 19462,418,437 Vogt Apr. 1, 1947 FOREIGN PATENTS Number Country Date 218,013Great Britain June 30, 1924

